has anyone tried the PGA2310 or Wolfson chip yet? - diyAudio
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Old 26th June 2002, 06:30 PM   #1
dorkus is offline dorkus  United States
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Default has anyone tried the PGA2310 or Wolfson chip yet?

if so, any comments on sound quality?
i've sorta given up on using an IC attenuator in Son of Dork but if someone has had success with them there may be hope yet...
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Old 26th June 2002, 07:44 PM   #2
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I am about 90% through with a design using the 2310. I also have some samples of the Wolfson part to try, but they will have to wait until the 2310 is done.

Unfortunately, like everything else, the last 10% takes 90% of the time/effort...

MR
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Old 26th June 2002, 08:51 PM   #3
rljones is offline rljones  United States
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FYI,

Rowland is now using PGA2310 in the Synergy preamp in place of the CS3310, for which it substitutes pin for pin, but runs off of a +/-15V supply rather than +/-5V, meaning less risk of overloading the inputs. (Both boards, however, require a +5V digital supply.)

As far as sound quality, I've heard both volume controls in my system, but I cannot say one chip is better than the other stictly on sonics as the new board with the PGA2310 also has a totally different topolgy. Having said that, I would most certainly use the PGA2310 over the CS3310 if only for the better overload protection: with 15V rails, the former can accept 27V peak to peak inputs.

I've had no experience with the Wolfson.

regards, robert
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Old 28th June 2002, 09:29 PM   #4
rljones is offline rljones  United States
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Default PGA2310 listening test

After this post, you guys got me to thinking. I have the old board from the Synergy II preamp, left over from the upgrade to the IIi, so maybe I could use it to test a PGA2310. I got to studying board to see how it worked, and I came up with a scheme that would require the least amount of fiddling. The results are very good!

First, the way I read the circuit board (some of this stuff is already published; Stereophile 9/99), it uses a Jensen JT10KBD input transformer that steps down the input signal 4:1. The balanced output of this transformer goes to one CS3310 run at +/-5V then onto a pair of opamps (with a DC servo), converting back to a balanced signal and then to a Jensen output transformer. The step down transformer is probably used to avoid overloading the CS3310 since it can only input/output 1.5V lower than each rail, or about 7Vp-p. Interestingly, there is a CS3310 per channel, and each one was used with one input grounded (ie, not fully balanced).

My idea was to replace the CS3310 with a PGA2310. As I studied it I got to thinking, why not use the PGA2310 fully balanced with each half (L/R) used for (+) signal leg and the other for the (-) leg. Also, since I was going to run it at +/-12V (21Vp-p), why bother with the input transformer? Since the output was inherently balanced, why use an output transformer? Moreover, as the PGA2310 already has an output buffer (bipolar and linear to 1.5MHz per spec sheet; maybe current feedback type?), why bother with the output buffer opamps? And finally, since the spec sheets quote a 0.5 mV offset, why have a DC servo?

So I removed essentially everything from the board, replaced the CS3310 with the PGA2310, cut a few traces, jumpered here and there, replaced the 7805 and 7905 with 12V versions, and added a 7805 for the digital voltage source. I replaced the IIi board in my Synergy with this modified II board after listening to the IIi for a few minutes, and then listened to the new unit that is actually only one PGA2310 per channel and nothing else.

The bottom line: it is great. The noise level dropped (why not?, two less transformers and two less op amps). The preamp is absolutely dead quiet. Dynamics are better and the soundstage is superior; in one SACD track I routinely use for testing, the singer's voice seems to now be really hanging out in front of the two speakers, perfectly centered and the depth is even better.

The bottom line is the PGA2310 is VERY good. It basically ends up being the entire preamp. Measured DC offset is 0.4 to 0.9 mV. You do need a source of less than 600 ohms to avoid increasing distortion (per spec sheet); but most sources fulfill this requirement. I do not know the output impedance, nor the current drive--does anybody have any information on this to share?--so if the output buffer is meager, then the PGA2310 could conceivably need another interface (opamp/mosfet source) with different loads or cables. In fairness, the input/output transformers may provide better rejection of RF interference and the like; I, however, have not noticed any problem since the change.

Regards, Robert

PS Sorry, Hugh, I keep getting side-tracked from building your AKSA amp. Soon, I promise.
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Old 28th June 2002, 10:51 PM   #5
mlloyd1 is offline mlloyd1  United States
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Robert:
Thanks, this was good input. I have been working on revising my preamp to use a 2310, but my honey-do list keeps expanding. At this rate, I'll have to wait for winter.
mlloyd1
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Old 29th June 2002, 05:05 AM   #6
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Default PGA2310 revisited

The PGA2310 digital volume control has been discussed at lenght since it was introduced. To find the old comments and on going projects for this device use the search feature of this site and seach for PGA2310.

Perhaps some of the old information is still usefull.

John Fassotte
Alaskan Audio
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Old 1st July 2002, 05:00 AM   #7
dorkus is offline dorkus  United States
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hey john,

already did a search, but no one i could find had really listened to the chip yet. but i've gotten some good responses so far in this thread.

dorkus
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Old 1st July 2002, 09:53 PM   #8
mlloyd1 is offline mlloyd1  United States
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Dorkus:
Did you ever see this?
http://www.mhennessy.f9.co.uk/
Click on the preamp and look for the main audio circuits

Quote:
Originally posted by dorkus
hey john,
already did a search, but no one i could find had really listened to the chip yet. ....dorkus
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Old 1st July 2002, 09:59 PM   #9
dorkus is offline dorkus  United States
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yup, seen that page before. isn't this the guy who poo-pooed the difference in sound quality between opamp ICs and liked the 5534 best? or i could be mistaken...
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Old 1st July 2002, 10:22 PM   #10
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Nah - I'm the guy who was able to admit that I couldn't hear a difference when I did the test! Brave, huh?

I also admitted that this might have been a defect in my hifi or my hearing. But, since then, I've upgraded my speakers and plan to repeat the tests soon. I try to keep an open mind.

(I had this reply on my webpage for a while, as I hadn't signed up to these forums at the time. It's still in Google's cache if you're interested. My comparison was limited to 5532 vs OPA2134)

I'm sorry if my webpage offended you. To return to the topic, I'm very pleased with the PGA2310. On my modest system, it's completely transparent. I'm almost ready to build the final version - just waiting for a collegue to etch the PCB's for me....

Cheers,

Mark
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